Viewing Interface in XCode 12.3

What sort of CocoaSlideshow have you downloaded? I cannot find one in Apple's pages.

I cannot display the interface in XCode.

Old apps may be using .xib (or .nib, if it's too old) instead of .storyboard.
Or the app may be constructing UI by code.

How can I display the interface in this project?

If you cannot find any in a buildable project, no way. The project may not have a visual interface definitions like storyboard or xib.

There is a .xib file. I recall editing the interface a few months ago but don't seem able to do it now after a few upgrades.

CocoaSlideShow was from Github.

I downloaded a zip of the CocoaSlideShow code from GitHub. The first time I viewed it with XCode (12.3.(12C33)) I could see the interface. After closing and re-opening I could not see it.

CocoaSlideShow was from Github.

I can find one CocoaSlideShow on Github, and it has only xibs.

I could see the interface. After closing and re-opening I could not see it.

Unless you accidentally deleted the xibs, you may be mistaking where to find it.

When I click on MainMenu.xib on the downloaded code, the interface appears OK. When I click on same file in the Modified code I don't see it and the message Unable to load Revisions appears and no interface is shown. What does this signify?

The modification I am trying to do is to add a pad region below the image, write some text entered in a text box in the pad region when a button is clicked. If I try and determine how to do this by setting a breakpoint where the image EXIF metadata is set, the call stack shown in the left pane contains what looks like assembler (Framework code) in the routine which calls the one in which the breakpoint is set. If I add a button, how can I make its click event execute the code to add padding to the image and write in it?

When I click on same file in the Modified code I don't see it and the message Unable to load Revisions appears

OK, please clarify:

• You can find MainMenu.xib in your project ( after modified).

• You cannot open or edit the MainMenu.xib in Xcode

• the message Unable to load Revisions appears <- ??? Where and when? When you try to open it? Or when build it?

how can I make its click event execute the code to add padding to the image and write in it?

Please do not ask two things in one thread.

MainMenu.xib is present in modified project. When I click on it I see in the left half of the centre pane some XML which I think describes the interface. In the right half is the message "No Editor". Below each half is the message "Unable to load revisions". In a pane below the two halves are a number of messages including "Failed to connect (Apply) outlet from (AppDelegate) to (NSButton): missing setter or instance variable". In the right-hand pane is the message "Not Applicable". Despite these problems the project builds and runs OK.

I am re-entering the project modifications to the downloaded code and so far the interface is visible when clicking MainMenu.xib.

When I click on it 

Please confirm, all you done is click on it, right?

the project builds and runs OK.

You have not written in any place that you Build or Run your project. How do you confirm the project builds and runs OK?
Please write everything you have done in your project.

Have you never touched Comparison button (⇄)?

I am re-entering the project modifications to the downloaded code and so far the interface is visible when clicking MainMenu.xib.

Seems you can work on it. Please remember everything you have done it, when you find something wrong in your project.